California Water Code section 10608.34, added by Senate Bill 555 in 2015, requires every urban retail water supplier to submit a validated water loss audit report to the Department of Water Resources.
Who files
An urban retail water supplier is a supplier that directly provides potable municipal water to more than 3,000 end users, or that supplies more than 3,000 acre-feet of water annually at retail for municipal purposes. A system below that is not covered by this section.
When
The statute set an October 1 deadline for suppliers reporting on a calendar year, through October 1, 2023, and a January 1 deadline for suppliers reporting on a fiscal year. From January 1, 2024 the date is January 1 of each year. A supplier that needs the operative text rather than a summary should read the section itself; a filing deadline is the kind of fact that moves by amendment.
What validation means here
The statute describes validation as a process in which the supplier uses a technical expert to confirm the basis of every data entry in the audit and to characterize the quality of the reported data. The audit follows the American Water Works Association method: the third edition of Manual M36 and the Free Water Audit Software.
Validation is why the California record carries a data validity score, and why the score matters more than the loss figure on its own. A validated audit is not a verified one: it is an audit whose inputs have been characterised, including the ones the supplier could not measure.
What the state publishes
DWR publishes the audits it receives. Two things about that file shape everything we do with it: its grain is the system-year rather than the supplier-year, so one investor-owned utility files a row per system it operates, and it carries columns naming individuals. That is why what we hold and cite is a redacted extract of it, identified by hash. Both are recorded in our sources.